Electric heater



May 29, 1928.

A. J. KERCHER ET AL ELECTRIC HEATER Filed March 10, 1924 2 Sheets-Sheet l llweuraes nan/0e .1. KBECHEE WILL/4M WESLEY Hicks. GYM

Patented May 29, 1928.

UNITED STATES PATENT OFFICE.

I AETHUEJ. KERCHEB, or BERKELEY, AND WILLIAM WESLEY Bronson sen .IRANCISCO, CALIFORNIA.

' ELECTRIC HEATER.

This invention relates to an electrically operated device for heating a room or the like. More particularly the invention refers to a heater that is arranged to produce a l movement of heated air to the desired calities. One form of such a convection type of heater is described and claimed in an application filed July 17, 1922, in the name of \Villiam \Vesley Hicks, entitled Electric 10 heater, and having Serial No. 575,543. The

present invention is an improvement over the apparatus shown in said application.

It is an object of the invention to improve in general the construction and operation of such convection type heaters.

In heaters of this character, there is sometimes used a heating unit supported on a hollow column of refractory material, such as clay. The unit itself is usually in the form of one or more long helical coils, which are in turn disposed in helical grooves in the periphery of the hollow support. These supports are most expeditiously moulded in two parts which arelater united, and are then subjected to the necessary heat treatmeat or curing process. Where a number of long helical coils is to be supported in grooves, there must be a helical groove for each of them, whereby the effect of a multiple thread screw is obtained, the pitch of each being high. In attempting to mould such high pitched grooves in the half supports by the use of patterns, it is found impossible to withdraw the pattern in one piece without destroying some of the thread configuration. It has therefore been necessary to make the pattern out of a sufliciently large number of separable pieces to effect the desired removal. It is still another object of our invention to make it possible to remove the'half-patterns in a single piece, by proper configuration of the grooves, which are made to depart from the helical form, but which nevertheless have slanting directions at least in some portions.

Our invention possesses other advantageous features, some ofwhich with the foregoing will be set forth at length in the following descriptiorr, where we shall outline in full that form of the invention which we have selected for illustration in the drawings accompanying and forming part of the present specification. Although we have shown in the drawings but one embodiment of our invention, we do not desire to be limited thereto, since the invention as expressed in tllie claims, may be embodied in other forms a so.

Referring to the drawings:

Figure 1 is a sectional view of a heater embodying our invention, and shown as installed in the wall of a room or the like;

Fig. 2 is an enlarged elevational view of one of the heating units shown in Fig. 1, but with'some of the grooves empty, so as 5 to show the structure more clearly;

Fig. 3 is a sectional view, the section being taken along the plane 3-3 of Fig. 2;

Fig. 4 is a sectional view of the heater shown in Fig. 1, the section being taken along plane 1-l of Fig. 1; and

Fig. 5 is a development of a portion of the periphery of the columnar support for the heating coils.

Referring to Figs. 1 and 4 more particu- 7 larly, the heater is shown asmounted in a recess 11 of a vertical wall. The front of the recess is covered by a. grill 12, appropriatelyheld in place with respect to the wall. Behind the grill 12 the heating ele- 30 ments 13 are supported, as'by the aid of a horizontal shelf 14 fastened to the back of the grill 12. This shelf has a vertical projection 15 which rises back of the elements 13, and also provides sides 16 '(Fig. 4), whereby the heater elements 13 are encompassed by the grill 12 and the vertical walls 15 and 16. The rear wall 15 curves over the top of the elements, as shown at 17 of Fig.

1, and is attached to the rear side of the grill 12. This curved portion, as well as the vertical walls 15, 16, serve to define an air passageway leading from the bottom of the grill 12, then back of the elements 13 and up to the top of grill 12. The rear wall of the passageway is formed by a sheet metal backing having a vertical wall 18, as well as a horizontal projection 19 connecting it to the rear surface of the grill 12. Its upper end 20 is curved forwardly to meet the upper portion of grill l2 and also to form a flaring passageway for the air. Side plates 21 are also provided, spaced from the sides 16, whereby the air passage has a U-shaped section as most clearly shown in Fig. 4.

As thus far described, it is evident that the air passageway in the rear of the elements 13, communicates with both the to and bottom portions of the grill 12, and forms a path for the cold air taken in at the bottom, which on'being heated, is expelled near the top of the grill 12. In this manner, convection currents of heated airare set up.

The elements 13 are most conveniently supported on the horizontal portion 14. In the present instance we show these elements as each comprising a hollow tubular member 22 of refractory material, as the support for the resistance coils 23 wound in grooves on its periphery. The member 22 has a flange or base 24 by the aid of which it may be fastened to the portion 14. The connections for the heater elements 13 may be most conveniently effected by the aid of a connection board 25 supported beneath the horizontal portion 14. In'this portion 1% there are apertures that register with the apertures through the supports 22, and in. this way, another passage for air is provided. This passageway extends from the lower portion of grill 12, through the elements 13,

and out again some distance below the top portion of grill 12. The air is rapidly heated in passing through elements 13, some at l'eastimpinging against the curved portion 17. This portion thus acts as a deflector; in addition, a large amount of heat is transferred to this curved portion, and the air in the rear passageway takes up some of this heat before passing out at the top of grill 12.

We ensure against the radiation of heat outside of the grilll2, so that all heat produced is substantially convective. QFor this purpose, that portion of the'grilling which is directly in front of the elements 13 has no apertures, and serves instead as a shield against the direct rays of the heaters. In order to utilize the radiant heat produced to the fullest extent, we provide a reflector 26 of thin copper, appropriately supported in =frontof the heaters 13 and formed with corrugations. These corrugations, besides increasing the reflecting surface, also serve to form additional vertical air passageways 27 (Fig, 4:) with which apertures in the shelf 14: register. The air in passing through these passageways takes up some of the heat that is not reflected back into the heated space surrounding the heaters 13. In this way, very efficient heating is possible, and in addition, the objectionable directly radiated'heat is suppressed or minimized.

The construction of the heaters .13 presents several highly novel and useful features, which are most clearly disclosed in Figs. 2, 3 and 5. The'coils 23 are accommodated in grooves 28 which circle around'the column 22, the grooves being formed by parallel spacing beads or mouldings extending around the periphery of the column. There are several independent grooves; in the present instance four. If these grooves were made helical, the pitch would be so great that in moulding the column 22, the pat-' ,prefer to make thein horizontal for the major portion of the circumference, and of high pitch for the remainder of the circum ference. Thus, referring toFig. 5, which is a development of the grooves, it isseen that in each complete circle there are only two places, indicated at 29 and 30, where the grooves 28 have a slanting direction; in other places, they are substantially horizontal. The entire pitch is taken up therefore in about one-third of the circumference.

Thus following the lower left hand groove 30, it extends horizontally for about 60 then it has a portion 31 having a steep upward pitch and which extends for another 60; then a horizontal portion 32 of about 120 is reached, which connects to a portion 33 that has another steep upward pitch and that extends for another 60 around the circumference; finally this groove extends'to a horizontal portion 34 that connects with the beginning 35 of another convolution. The three other grooves are similarly formed. The rogress of the grooves axially is thus step-'iiy-step, instead of uniform.

The effect of formin the grooves with only a small portion hdlical, on the process of withdrawing the pattern is best appreciated from a consideration of Fig. 3. In this figure, the column 22 is shown as split in two equal parts by the diametrical line 36. The split is'also indicated by the line 37 of Fig. 5; and in fact we prefer to mould the column in this way and then afterward to unite these halves by manual application of plastic material. The half-columns are so arranged that the helical portions of the grooves occupy a central position thereon. As the pattern is withdrawn its movement is substantially radial to that part of the periphery carrying the slanting grooves, and there is thus no diificulty in freeing the pattern. If the slanting portions extendednear to the edges, the freeing movement of the pattern would be tangential to the periphery, and the slanting corrugations forming the grooves would interfere with this withdrawal. However, horizontal corrugations offer no resistance at these points as is evident.

The grooves in column 22 as indicated most clearly at 38 in Fig. 2, are paired off near the top, so that one groove connects with another adjacent one. In this way, it

is possible to double back a long-helical coil of wire 23 through both connected grooves, and thus to overcome the effects of self-induction in k the winding. Furthermore, proper provisions such as apertures near the ottom of the column may be provided for leading in connections to the heater coils from the central cored aperture 39.

We claim:

1. As an article of manufacture, a refractory support for a heating element, comprising a column of circular cross section, with one or more grooves encircling the periphcry, for accommodating conductors to be heated, said grooves in making a complete turn around the column having a pair of slanting portions on 'diametrical opposite sides of the column and providing the axial progress of the grooves, said slantin portions being connected by portions having no substantial axial rise.

2. An electrical heatin element for heating a fluid medium by radiation and convection, comprising an elongated core of refractory material, one or more ribs of unbroken continuity running progressively about the core to form one or more grooves upon the core periphery, said ribs being formed as an integral part of the refractory core and having portions running substantially parallel to a plane normal to the core axis and other portions running at an angle to said plane, and one or more convoluted resistance conductors disposed in the grooves formed by said ribs, said ribs forming broken insulating walls between adjacent loops of said conductors.

3. A heating element comprising a refractory core, at least two continuous ribs encircling the periphery of the core from one end to the other thereof, said ribs being substantially normal to the axis of the core for a major portion of the periphery and being inclined to said axis for a minor portion of the periphery, the ribs on said latter portion having overlapping ends as measured in the general direction of the axis of the core, and a resistance conductor positioned in the grooves defined by said ribs.

4. A heating element comprising a hollow cylindrical core of refractory material, a convoluted resistance conductor wound about said core and doubled upon itself whereby the ends of the conductor terminate at the same end of the core, and a lurality of continuous ribs formed upon t e periphery of the core, said ribs having portions running substantially parallel to a plane normal to the core and, other portions running at an angle to said plane, said ribs forming unbroken insulating walls between the doubled lengths of said conductor.

In testimony whereof, we have hereunto set our hands.

' ARTHUR J. KERCHER.

WILLIAM WESLEY HICKS. 

